Attention has been defined as a focusing of consciousness, or, if one prefers the form of expression, as "detention in consciousness." In the first case, we may liken it to the action of the sun-glass through which the sun's rays are concentrated upon an object, the result being that the heat is gathered together at a small given point, the intensity of the same being raised many degrees until the heat is sufficient to burn a piece of wood, or evaporate water. If the rays were not focused, the same rays and heat would have been scattered over a large surface, and the effect and power lessened. And so it is with the mind. If it is allowed to scatter itself over the entire field of a subject, it will exert but little power and the results will be weak. But if it is passed through the sun-glass of attention, and focused first over one part, and then over another, and so on, the matter may be mastered in detail, and a result accomplished that will seem little less than marvelous to those who do not know the secret. _Thompson_ has said: "The experiences most permanently impressed upon consciousness, are those upon which the greatest amount of attention has been fixed." Another writer upon the subject has said that "Attention is so essentially necessary to understanding, that without some degree of it the ideas and perceptions that pass through the mind seem to leave no trace behind them." _Hamilton_ has said: "An act of attention, that is, an act of concentration, seems thus necessary to every exertion of consciousness, as a certain contraction of the pupil is requisite to every exertion of vision. Attention then is to consciousness what the contraction of the pupil is to sight, or, to the eye of the mind what the microscope or telescope is to the bodily eye. It constitutes the better half of all intellectual power." And _Brodie_ adds, quite forcibly: "It is Attention much more than any difference in the abstract power of reasoning, which constitutes the vast difference which exists between minds of different individuals." _Butler_ gives us this important testimony: "The most important intellectual habit I know of is the habit of attending exclusively to the matter in hand. It is commonly said that genius cannot be infused by education, yet this power of concentrated attention, which belongs as a part of his gift to every great discoverer, is unquestionably capable of almost indefinite augmentation by resolute practice." And, concluding this review of opinions, and endorsements of that which the Yogis have so much to say, and to which they attach so much importance, let us listen to the words of _Beattie_, who says: "The force wherewith anything strikes the mind, is generally in proportion to the degree of attention bestowed upon it. Moreover, the great art of memory is attention, and inattentive people always have bad memories."